They emphasize that sharks play a critical role in marine ecosystems, ensuring the long-term health and stability of fisheries and, in turn, economies.

Sharks are top predators, which means they maintain checks and balances on other species by feeding on sick or weak fish, seals, and other marine life. But sharks are slow to breed and are being overfished.

In the absence of sharks, populations of certain other species can mushroom, depleting some marine regions of resources needed to sustain ecosystem balance.

Tolon and 30 other fishers in his community are helping Iemanya Oceanica track the size and species of sharks in the Pacific Ocean and the Gulf of California, the two bodies of water divided by the Baja California peninsula.

They continue to hunt Galápagos, hammerhead, blue, and whale sharks, but make sure to release pregnant and young animals, Tolon said.

Iemanya Oceanica's executive director Laleh Mohajerani said involving fishing communities in research is an important conservation tool.

"What we want to do is give the fishers ownership over the management of their resources," said Mohajerani, whose work is funded in part by the National Geographic Society's Conservation Trust. (The National Geographic Society owns National Geographic News.)

"By logging their catches, they see in an even more direct way how far the shark stocks have fallen."

"It has not been easy," she added. Some fishers are resistant to ending their harvest of sharks now for a possible payoff later.

Sustainable Economies

Peter Klimley, a shark expert based at the University of California, Davis, believes groups like Iemanya Oceanica can succeed if indigenous fishers start to see sharks as a renewable resource, and if certain areas become off-limits to fishing.

"What makes the decline so poignant is that there's so much interest in ecotourism to dive with them," said Klimley, who has received funding from the National Geographic Society's Expeditions Council for his own research on hammerhead sharks.

"We're in a transition where people are beginning to see these animals as something beautiful."

The economic transformation has worked in several Mexican seaside communities that used to rely on hunting sea turtles but have now switched to ecotourism.

Local shark fisher Tolon is hoping to set an example by diversifying his business.

"We hope to preserve our communities by doing this," Tolon added. "But we need help from our government to build an infrastructure for tourists—to convert our boats, build campgrounds, motels, and restaurants."

He'd also like to sell his catch directly to people in Mexico City.

"We'd make more money that way. But we haven't yet organized to do that."

Patrolling the Seas

Some species would benefit from being on government lists of protected species.

In 2007, for example, the Mexican government placed the great white shark on a list of protected species. It is now illegal to reel in the great white, once one of the fishers' prized catches because of its size.

But Klimley and Tolon agree that classification won't change the situation without patrols, similar to the way Mexico assigns patrols to protect sea turtles.

They recognize that patrolling beaches where female turtles spawn is a far easier task than sending naval patrols to protect the shark habitat in the waters that flank the Baja California peninsula.

Even so, Tolon said, "within five years, we'll have a disaster in the coastal communities without vigilance. We need those patrols. Without them, we'll soon be lost, in spite of the best efforts of those who are helping us."